digestate management in flanders: nutrient removal … · iii. digestate management in flanders:...
TRANSCRIPT
DIGESTATE MANAGEMENT IN FLANDERS: Nutrient removal versus nutrient recovery
BioGasWorld, Berlin
25/04/13
Sara Van Elsacker, VCMFrederic Accoe, Viooltje Lebuf, VCMCéline Vaneeckhaute, Evi Michels, Erik Meers, UGent
CONTENT
I. Introduction VCM
II. Biogasproduction in Flanders
III. Digestate management in Flanders
IV. Why recover nutrients?
V. Nutrient recovery techniques
VI. End-products
VII. Need for further research
VIII. Conclusions
IX. Related projects
X. ManuREsource
I. INTRODUCTION VCM
Flemish Coordination Centre for Manure processing (VCM)
Independent platform and intermediate between government and the manure processing sector
Activities
Platform:
to coordinate consultation between government and private sector
Policy support
Yearly enquiry on processing capacity and techniques
Detecting bottlenecks and suggesting solutions
Thematic studies (e.g. preparation of new legislation)
First line support
Selection of technology, regulatory aspects, environmental permits, ...
Knowledge centre
All aspects of manure processing (technical, regulatory, economic)
Focus on recovery and valorization of nutrients
II. BIOGASPRODUCTION IN FLANDERS
35 biogas plants (active in 2011) in Flanders
1 744 300 Ton input/year 70.3 MWe/year installed
300 GWhe green energy
27 biogas plants have manure input
400 000 Ton manure/year digested
III. DIGESTATE MANAGEMENT IN FLANDERS
III. DIGESTATE MANAGEMENT IN FLANDERS: situation
Organic and inorganic fertilisers water pollution
European Nitrate Directive (1991)
Limit nutrient dosage on fields
Strong limit on animal manure (170 kg N/ha)
Biogas-installations that take in manure Digestateequals animal manure status
Raw digestate disposal is difficult, esp. in nutrient rich regions (West-Flanders, Antwerp)
Most co-digestion plants invest in digestateprocessing techniques
III. DIGESTATE MANAGEMENT IN FLANDERS: situation
III. DIGESTATE MANAGEMENT IN FLANDERS: manure processing
Biological treatment
Drying
Pelletizing
Solid manure
Liquid fraction
Composting
Liming
Liquid manure
Electrolysis
Mechanical separation
Solid fraction
Ammonia stripping
Liming
Membrane Filtration
Evaporation/condensation
Constructed
wetlands
III. DIGESTATE MANAGEMENT IN FLANDERS: digestate processing
Digestate
938.700 ton1
36 AD plants2
Drying Composting
Separation
Export
Pellets
Third party disposal
...1 Vlaco activity report 20112 VCM survey 2011, Progress report Biogas-e 2011
Composting
III. DIGESTATE MANAGEMENT IN FLANDERS: digestate processing
8
2
23
3
0 10 20 30
Drying
Composting
Separation
Third partydisposal
Digestate
AD plants
III. DIGESTATE MANAGEMENT IN FLANDERS: SF Digestate
Solid fraction
Third party disposal CompostingDrying
Export
Pellets
Export
Pellets
CompostingComposting
III. DIGESTATE MANAGEMENT IN FLANDERS: sf digestate
13
3
7
0 5 10 15
Drying
Composting
Third party disposal
Solid fraction
AD plants
III. DIGESTATE MANAGEMENT IN FLANDERS: lf digestate
Liquid fraction
Biological
nitrification/
denitrification
Membrane
filtrationEvaporation
Agriculture
Agriculture
Filtration
NH3 stripping
EvaporationExport
Agriculture
Agriculture
Third party disposal
Membrane
filtration
Biological
nitrification/
denitrification
III. DIGESTATE MANAGEMENT IN FLANDERS: lf digestate
1
4
6
9
11
0 2 4 6 8 10 12
NH3 stripping
Third party disposal
Membrane filtration
Biological nitr/denitr
Evaporation
Liquid fraction
AD plants
IV. WHY RECOVER NUTRIENTS?
Awareness of phosphorus depletion
Awareness of increasing artificial fertiliser use
Energy consuming
Economical burden for farmer
Question: how can digestate be valorised as a valuable source of nutrients?
OR: how can digestate be turned into a ‘green’ substitute for artificial fertilisers?
Extract nutrients!
V. NUTRIENT RECOVERY TECHNIQUES
Hard to define
Interpretation:
End-product with a higher concentration of NPK than raw digestate
Techniques that separate NPK of organic matter
Goal: end-product that can substitute artificial fertiliser or as a feedstock in industrial processes
IV. Nutrient recovery techniques
V. NRT (1): Acid air washer
Drying, composting, evaporation, ...
Important: treat drying gases!
Dust, ammonia, odorous gases
Acid air washer that captivates NH3
End-product: (NH4)2SO4
Flanders: artificial fertiliser
Variable N-content
Low pH, high salt content
Sulphur content
Status: full scale
Restrains use
V. NRT(6): Ammonia stripping
Aeration in packed column
Elevated pH & T
Bottlenecks: precipitation of salts & fouling of the packing material, periodical cleaning necessary
Acid air washer
Stripgas + sulphuric acid ammonia sulphate
Higher N-content than air washer drying gases/stables
Lime softening step with Ca(OH)2
Removes Ca2+, Mg2+, carbonates
Preferred pH-increase
Status
Full-scale
V.NRT(2): Extraction of organically bound P
Ashes: P-, K-, Al- & Si-components + heavy metals (Cu, Zn, Cd)
Several processes
Thermochemical
Addition of MgCl2 & heating up to 1000°C
Heavy metals in the gaseous phase
Production of e.g. CaHPO4
Wet-chemical extraction techniques
Acid extraction
Fertilising value (Kuligowski et al., 2010)
Status
Full scale for ashes of sludge WWT, poultry manure (NL)
Lab scale testing
V. NRT(3): Pressurised membrane filtration
Types
Pressure: RO > UF > MF
Pore size: MF > UF > RO
Concentrate: suspended solids (MF), macromolecules (UF), ions (RO)
Other pre-treatment: DAF (+ flocculants)
Bottleneck: blocking of membranes
Suspended solids, salts with reduced solubility, biofouling
Higher tangential flux, anti-scalants, cleaning agents (NaOH & H2SO4)
Pilots mineral concentrates (NL)
Agronomic, economic & environmental effects of MC
Goal: recognition as an artificial fertiliser
EU 2003/2003 (EU-fertiliser)
Nitrate Directive
Status: full-scale (4 biogas plants in Flanders)
V. NRT(4): Other membrane techniques
Forward osmosis
Draw solution in stead of pressure
Status
Full-scale in other sectors, no testing (?) with digestate
Electrodialysis
Ion exchange membrane + electrical voltage
Transfer of NH4+, K+ en HCO3
-
Status
No full-scale on digestate, tests on lab-scale in literature
Transmembrane chemosorption
Innovative pig slurry treatment in NL
Gaseous NH3 diffuses through membrane & is captured in sulphuric acid
Status: pilot in NL
V. NRT (5): P-precipitation
Soluble P (ortho-phosphate) can be precipitated by:
Ca2+ Ca3(PO4)2
Mg2+MgNH4PO4 or MgKPO4 (MAP of struvite)
K+ K2NH4PO4 (potassium-struvite)
Commercial processes in development:
Reactors
Large, pure crystals (seeding)
Full-scale in WWT
Status: full-scale for calf manure and in other sectors + pilot testing on digestate
Optional: dissolve organically bound P
Acid extraction
Creates a P-low solid fraction
V. NRT (7): Biomass production & harvest
Research on algae & duckweed
Removal of P&N by plant uptake
Bottleneck: suspended solids, humic acids,... reduction of penetration of light
Max. additions in growing medium
Large surface
Valorising harvested biomass
Biobased chemicals
Biofuels
Fertilisation
Feed (GMP)
Status
Lab tests + pilot on duckweed
VI. END-PRODUCTS
TECHNIQUE STARTING FROM END-PRODUCT CHARACTERISTICS
Acid air washer Air charged with NH3 (NH4)2SO4 solution(NH4)2SO4 solution :
30-70 kg N/m³, pH 3-7
P-extraction Ashes/biochar/SF digestate Acid P-extract/CaHPO4
Acid P-extract: Ptot: 0.192 g/kg
Reversed osmosis UF/MF/DAF-permeateRO-concentrate (NK-
fertiliser)
Ntot: 7.3 g/kgKtot: 2.9 g/kg
Ptot: 0.42 g/kg
Forward osmosis UF/MF/DAF-permeateFO-concentrate (NK-
fertiliser) ?
Electrodialysis LF digestate NK-fertiliser ?
TMCS LF filtered on 10 µm NK-fertiliser(NH4)2SO4 solution:
50 - 150 kg N/m³
P-precipitation (LF) digestateMgNH4PO4/MgKPO4/CaN
H4PO4
12.65/11.62/11.86% P
NH3-stripping & acid air washer
LF digestate (NH4)2SO4 solution30-70 kg N/m³
pH: 3-7
Biomass production Diluted LF digestate Biomass Duckweed: 30% CP (dm)
VII. NEED FOR FURTHER RESEARCH
Technical bottlenecks
WWT-techniques translated to digestate bottlenecks
Marketing
Added value of the end-product vs investment to be made
End-users: farmers or industrial users?
Legislative
Redefine “artificial fertiliser”
Sustainability
Comparative analysis of environmental impact (LCA)
Consumption of heat, electricity & chemicals, risk for emissions
Reduction of the artificial fertiliser use
VIII. CONCLUSIONS
High nutrient pressure + P depletion
Digestate treatment is inevitable
As a valuable source of nutrients
Techniques
Full-scale
Acid air washers, membrane filtration, ammonia stripping
Breakthrough full-scale
Struvite precipitation
Potentially long-term
Electrodialysis, forward osmosis, TMCS, biomass production
Questionmark
P-extraction from ashes/biochars
Further developments will only take place if recovery is profitable
Price for recuperated nutrients = price for nutrients in artificial fertilisers
IX. RELATED PROJECTS
ARBOR
Interreg IV.B
Accelerate development of renewable energy in NW-Europe
Inventory of nutrient recovery techniques + LCA + EA
Characterisation of end-products
Field trials
Market study
MIP Nutricycle
Flemish project
Produce artificial fertiliser replacers
Pilots on ammonia stripping & preconditioned separation
Lab tests with struvite
BIOREFINE
Interreg IV.B, kick-off meeting 3/2013
Nutrient recycling
European platforms : Transnational cooperation to identify and solve bottlenecks
International conference onManure management and valorization
December 5-6, 2013 - Bruges, Belgium
ManuREsource 2013
www.manuresource2013.org
